The target for GPs to guarantee patients an appointment within 48 hours should be restored to help ease the pressure on accident and emergency departments, shadow health secretary Andy Burnham said.
Mr Burnham indicated that reintroducing the 48-hour pledge, which was scrapped within months of the coalition taking office, could be put before the Commons for a vote next week.
He was speaking as health workers revealed the pressures on A&E services at a meeting organised by Labour in Parliament.
Mr Burnham said: "It is now clear that 2013 has been the worst year in a decade in A&E. The pressure that we have seen all year hasn't abated. In recent weeks it has been running at winter levels before winter has begun in earnest.
"So there are genuine concerns now about the service's ability to cope over what we expect will be a very difficult winter."
Ahead of next week's opposition motion on the pressures facing A&E, Mr Burnham said the 48-hour pledge was introduced by Labour but scrapped in June 2010.
"I think that we should bring that back," he said and indicated it could be "at the centre of our opposition day debate".
Many of the pressures on A&E units have been blamed on patients going to hospital because they are unable to see a GP.
The meeting heard from senior A&E nurse Angela Bartholomew who told Mr Burnham that she spent most of her time "fire fighting" as a result of the crisis in emergency services.
She said the money being put into A&E was "great" but "I just feel like we are fire fighting, it's crisis management constantly".
It was a "regular thing" for the department to be understaffed, she said. "We have been able to backfill with agency (nurses) but that costs a lot of money, it's not financially viable to continue like that.
"It's pretty much nearly every other shift you are faced with staffing problems. Agency staff, some of them are incredibly good but some of them have never worked in our department before, so that's a challenge in itself.
"I would like to see something done about the staffing levels, that's one thing that is crucial. If we are going to operate like this then we need to have the staff to be able to take care of people."
Michelle Goodman, a nurse with the NHS 111 service, said some patients would be referred to A&E units with toothache.
"They are actually going to be advised to go to A&E, which is not going to be the right place for them to go and you almost think 'you don't need to send them there'.
"But that is part of a pathway that's going to be introduced in some areas ... totally inappropriate, so we need to be looking at somehow providing services for people who have some sort of dental crisis out of hours."
In response to concerns being raised about the use of private and voluntary ambulances, Mr Burnham said it went against the plan set out by NHS medical director Professor Sir Bruce Keogh who wanted them to be skilled ''mobile urgent treatment services, not just urgent transport services".
Mr Burnham said: "It seems to me that most ambulance services are going in precisely the opposite direction to the one recommended by the Keogh review."